A device for a vehicle drivetrain with a power branching transmission and a reversing or turnover gear system is known from DE 10 2007 018 999 A1. A drive input of the power branching transmission drives a planetary gear unit via the reversing gearing, in the area of which the power is divided between a hydraulic power branch and a mechanical power branch. The hydraulic power branch consists of a pump and two motors. In addition, a hydraulic supply pump is connected to the drive of the power branching transmission, which supplies pressure fluid to the closed circuit of the hydraulic pump and hydraulic motors in the sense of a feed pump.
Disadvantageously, however, neither in traction operation nor in thrust operation can a drive torque be produced at the drive output of a vehicle drivetrain or an applied drive output torque be supported by means of the additional hydraulic device or the hydraulic supply pump. Moreover, by means of the hydraulic device no recuperative operation can be carried out, during which a thrust torque in the drivetrain can be used to recover energy and by virtue of which a vehicle can be operated more efficiently.
A hydrostatic drive with which braking energy can be recovered is described in DE 10 2006 060 014 A1. The hydrostatic drive is formed with a hydro-pump and a hydro-motor connected to one another by a first and a second working line. Furthermore, the hydrostatic drive is made with a first reservoir and a second reservoir, the first reservoir being designed for the storage of pressure energy and being connected to the first working line by a first seat valve and to the second working line by a second seat valve. The second reservoir can be connected to the first working line by a third seat valve and to a second working line by a fourth seat valve.
Disadvantageously, this hydrostatic drive is characterized by a complex structure and high production costs, for which reasons the drive is only of restricted suitability for use in a hybrid vehicle drivetrain.